1. Technical Field
The present invention relates generally to computer networks and more particularly to a method and system for monitoring and collecting data in a client-server computer network such as the Internet.
2. Description of the Related Art
The World Wide Web is the Internet's multimedia information retrieval system. In the Web environment, client machines effect transactions to Web servers using the Hypertext Transfer Protocol (HTTP), which is a known application protocol providing users access to files (e.g., text, graphics, images, sound, video, etc.) using a standard page description language known as Hypertext Markup Language (HTML). HTML provides basic document formatting and allows the developer to specify "links" to other servers and files. In the Internet paradigm, a network path to a server is identified by a so-called Uniform Resource Locator (URL) having a special syntax for defining a network connection. Use of an HTML-compatible browser (e.g., Netscape Navigator or Microsoft Internet Explorer) at a client machine involves specification of a link via the URL. In response, the client makes a request to the server identified in the link and receives in return a document formatted according to HTML.
The time period between the issuing of an HTTP request from the browser and the return of the requested document (or some component thereof) is known as the end user "response time." The response time is a function of the time spent servicing the HTTP request at the Web server together with the network transmission time to and from the server. The network transmission time is sometimes referred to herein as the "Internet delay."
Response times could be measured in environments where the clocks of the client and server machines are synchronized or where an external time reference is available to both the client and the server. Given the diverse nature of the Internet environment, however, such solutions are impractical because these criteria could not be met for all of the clients of a large web server. One possible alternative would be to place a special client (a so-called "transaction monitor") on the Internet and have the transaction monitor periodically issue a request to the server of interest. The transaction monitor would have to be built with response time instrumentation applied. Measured response times for this client would then be presumed to be indicative of response times that actual clients encountered. Such an approach also has significant drawbacks. The transaction monitor would presumably hook into the Internet at a fixed site or ISP (or at most a small number of sites). The response times measured by the transaction monitor would thus represent only a small fraction of the total paths that may be used to connect to a large server. In addition, such a transaction monitor would be useless for resolving questions about the response times for requests issued by way of an ISP that the transaction monitor is not currently using. Further, the transaction monitor would have to be constructed to use test transactions against the server. Test transactions are suspect in that they may omit entire classes of operations, and they can be difficult to create if the mission of the Web server is considered critical or secure (e.g., financial transactions).
There remains a need to provide an end user response time monitor that overcomes these and other problems associated with the known prior art.